Generation of wrinkle-free silicon monoxide electrodes using separate preformation and formation

ABSTRACT

A solid electrolyte interface is formed on a silicon monoxide electrode in a battery cell. After the solid electrolyte interface is formed on the silicon monoxide electrode, the battery cell is charged for one or more initial cycles while the battery cell is compressed.

BACKGROUND OF THE INVENTION

New types of battery cells with silicon-based (e.g., silicon monoxide(SiO)) electrodes are being developed because they have the potentialfor better energy density and/or capacity compared to graphite-basedelectrodes. As a result of their new composition (i.e., silicon-basedinstead of graphite-based), new techniques for producing battery cellswith silicon-based electrodes must be developed. Naturally, it would bedesirable if such new production techniques resulted in high qualitybattery cells, for example with desirable electrical and/or physicalcharacteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention are disclosed in the followingdetailed description and the accompanying drawings.

FIG. 1 is a flowchart illustrating an embodiment of a process to producea wrinkle-free silicon monoxide electrode using separate preformationand formation steps.

FIG. 2 is a diagram illustrating an embodiment of a cross section of abattery cell before and after a solid electrolyte interface (SEI) isgrown during a preformation step.

FIG. 3 is a diagram illustrating an embodiment of a cross section of awrinkled electrode and a flat electrode.

FIG. 4 is a diagram illustrating an embodiment of equipment used toproduce a battery cell with a flat electrode.

FIG. 5 is a flowchart illustrating an embodiment of battery cellproduction process with separate preformation and formation steps.

FIG. 6 is a diagram illustrating an embodiment of a preformation stepduring which a solid electrolyte interface (SEI) is grown.

FIG. 7 is a diagram illustrating an embodiment of a process to form asolid electrolyte interface over at least two cycles of battery cellcharging.

FIG. 8 is a diagram illustrating an embodiment of a process to form asolid electrolyte interface over at least two cycles of battery cellcharging over different amounts of time and up to different voltages.

FIG. 9 is a diagram illustrating an embodiment of a formation stepduring which an electrode is charged for the first time.

FIG. 10 is a flowchart illustrating an embodiment of a process to chargean electrolyte for one or more initial cycles while a battery cell iscompressed.

FIG. 11 is a diagram illustrating an embodiment of a high pressure step.

FIG. 12 is a flowchart illustrating an embodiment of a process toproduce a wrinkle-free silicon monoxide electrode using separatepreformation and formation steps and brief, high compression steps.

DETAILED DESCRIPTION

The invention can be implemented in numerous ways, including as aprocess; an apparatus; a system; a composition of matter; a computerprogram product embodied on a computer readable storage medium; and/or aprocessor, such as a processor configured to execute instructions storedon and/or provided by a memory coupled to the processor. In thisspecification, these implementations, or any other form that theinvention may take, may be referred to as techniques. In general, theorder of the steps of disclosed processes may be altered within thescope of the invention. Unless stated otherwise, a component such as aprocessor or a memory described as being configured to perform a taskmay be implemented as a general component that is temporarily configuredto perform the task at a given time or a specific component that ismanufactured to perform the task. As used herein, the term ‘processor’refers to one or more devices, circuits, and/or processing coresconfigured to process data, such as computer program instructions.

A detailed description of one or more embodiments of the invention isprovided below along with accompanying figures that illustrate theprinciples of the invention. The invention is described in connectionwith such embodiments, but the invention is not limited to anyembodiment. The scope of the invention is limited only by the claims andthe invention encompasses numerous alternatives, modifications andequivalents. Numerous specific details are set forth in the followingdescription in order to provide a thorough understanding of theinvention. These details are provided for the purpose of example and theinvention may be practiced according to the claims without some or allof these specific details. For the purpose of clarity, technicalmaterial that is known in the technical fields related to the inventionhas not been described in detail so that the invention is notunnecessarily obscured.

Various embodiments of a technique to produce a wrinkle-free siliconmonoxide electrode using separate preformation and formation steps aredescribed herein. In some embodiments, this is done by forming a solidelectrolyte interface on a silicon monoxide electrode in a battery celland after the solid electrolyte interface is formed on the siliconmonoxide electrode, charging the battery cell for a first time while thebattery cell is compressed. The step of forming a solid electrolyteinterface on an electrode (e.g., a SiO anode or cathode) is referred toherein as the preformation step. The step of charging the battery cellsfor the first time is referred to herein as the formation step. As willbe described in more detail below, by compressing the battery cell (andeverything in it) during the formation step, a wrinkle-free battery cellis produced.

FIG. 1 is a flowchart illustrating an embodiment of a process to producea wrinkle-free silicon monoxide electrode using separate preformationand formation steps. As will be described in more detail below, thisprocess produces a solid electrolyte interface (SEI) with goodelectrical and/or physical properties or characteristics, such as lowresistance, good proximity, etc.

At 100, a solid electrolyte interface (SEI) is formed on a siliconmonoxide (SiO) electrode in a battery cell. An example of this isdescribed in more detail below where the battery cell is filled withliquid electrolyte (e.g., a lithium-based liquid electrolyte, such as acombination of ethylene carbonate (EC), ethyl-methyl carbonates (EMC),and/or dimethyl carbonate (DMC), as well as lithium hexafluorophosphate(LiPF6)). The solid electrolyte interface is then gradually formed byapplying a charging current to the battery cell (e.g., multiple times).This causes the liquid electrolyte in contact with the electrodes (e.g.,a SiO anode and a cathode) to change from a liquid state to a solidstate with the thickness of the SEI gradually increasing. As describedabove, step 100 is referred to as the preformation step.

At 102, after the solid electrolyte interface is formed on the siliconmonoxide electrode, the battery cell is charged for one or more initialcycles while the battery cell is compressed. By applying pressure to thebattery cell while the SEI is charged for the first n times (e.g., wheren≥1), all of the layers within the battery cell (e.g., the separator,the SiO anode, etc.) which result or are otherwise produced will be flatand not wrinkled. As described above, step 102 is referred to as thepreformation step.

The following figure shows an example of the layers in a battery cellinvolved in a preformation step.

FIG. 2 is a diagram illustrating an embodiment of a cross section of abattery cell before and after a solid electrolyte interface (SEI) isgrown during a preformation step. In the example shown, diagram 200shows the battery cell before the battery cell has been filled withliquid electrolyte and before the SEI has formed. In the state shown,there is a cathode (202 a) and a SiO anode (204 a) with a separator(206) between the two electrodes. In this example, the separatorprovides a physical barrier which prevents the cathode and anode fromtouching, which would create a short circuit. As the close up view (210a) shows, both the cathode (202 a) and anode (204 a) have pores in them.

Diagram 220 shows the battery cell after it has been filled with aliquid electrolyte (222) and the SEI (224) has been formed. The SEI(224) forms from the liquid electrolyte (222) when a charging current isapplied to the battery cell (e.g., over multiple cycles). The SEI beginsgrowing where the liquid electrolyte comes into contact with the cathode(202 b) and the SiO anode (204 b). As more of the liquid electrolytechanges state from liquid to solid, the SEI continues to grow and thethickness of the SEI increases. As close up view 210 b shows, the liquidelectrolyte (222) permeates the pores of the cathode and anode and thesolid electrolyte interface (224) also forms in those pores.

The following figure shows an example of a flat (i.e., good) electrodeand a wrinkled (i.e., bad) electrode.

FIG. 3 is a diagram illustrating an embodiment of a cross section of awrinkled electrode and a flat electrode. In the example shown, diagram300 shows a battery cell with wrinkled electrodes (306) (i.e., awrinkled cathode (302) and a wrinkled SiO anode (304)). As shown here,the wrinkled electrodes tend to increase the distance between the twoelectrodes (in this example, represented by d_(wrinkled)), in particularwhere the wrinkling creates a void or concave region where one electrode(e.g., the SiO anode) pulls away from the other electrode (e.g., thecathode). This is also seen in close up view 310. This wrinkling hasbeen particularly observed with SiO anodes. Electrically, this isundesirable because the charge produced by the battery cell flows fromone electrode to the other (e.g., through the increased distanced_(wrinkled)) and so the battery cell cannot produce as high of acurrent when the anode and cathode have poor proximity because it ismore difficult for the charge to cross the increased distance. Thisincreased separation is sometimes referred to herein as poor proximity.

Diagram 320 shows an example of a battery cell with flat electrodes(326) (i.e., a flat cathode (322) and a flat SiO anode (324)). As shownhere, there are no voids or concave regions in the electrode (326). Thisis also shown in close up view 330. The flat electrodes mean that theelectrodes (i.e., the cathode (322) and SiO anode (324)) have goodproximity with each other. That is, the distance between the flatelectrodes (i.e., d_(flat)) is less than the distance between thewrinkled electrodes (i.e., d_(wrinkled), where d_(wrinkled)>d_(flat)).This, in turn, results in a battery cell with good electricalperformance. Generally speaking, a battery cell with flat electrodes(i.e., with good proximity) is able to output a higher current than abattery cell with wrinkled electrodes (i.e., with poor proximity). Forthis reason, techniques which help to produce a flat electrode with goodproximity are desirable.

Returning briefly to FIG. 1, the process shown there helps to produce aflat electrode (anode in this case) as opposed to a wrinkled electrode.The materials in the battery cell expand and contract but do so atdifferent rates (e.g., some materials have large volumetric changeswhile others do not expand and contract as much), which results in awrinkled electrode as different materials repeatedly expand and contractat different rates. By applying pressure to the battery cell when thebattery cell is charged for the first few times (e.g., at step 102), aflatter electrode is produced.

The following figure shows an example of a system which may be used toproduce a battery cell per techniques described herein.

FIG. 4 is a diagram illustrating an embodiment of equipment used toproduce a battery cell with a flat electrode. A battery cell beingproduced or manufactured may be swapped out between the two pieces ofequipment shown here depending upon what a given production step callsfor.

Diagram 400 shows an example of a system which applies pressure and/orcharge to a battery cell. In this example, a battery cell (402) isinside of a clamp which includes rigid fiberglass (404) and stiff foam(406). The stiff foam may be useful because it transfers most of thepressure from the press to the battery cell, but has some “give” toprevent damage to the battery cell. In FIG. 1, the press may be used toapply compress the battery cell at step 102.

The system shown in diagram 400 also includes a constant current source(408) which generates a constant current (410) which is used to chargethe battery cell (402). This application of a constant current may beused to form an SEI (e.g., during a preformation step) and/or to chargethe battery cell for the first time (e.g., during a formation step). Forexample, in FIG. 1, the constant current source may be used to chargethe battery cell at step 102.

To discharge the battery cell (e.g., if/when called for by some batterycell production process), the switches (412) are configured so that theconnection between the constant current source (408) and battery cell(402) is disconnected and the connection between the load (414) andbattery cell (402) is connected. This permits the battery cell todischarge by sending charge from the battery (416) to the load (414).For example, some production processes include multiple cycles ofcharging and discharging, so the switches (412) would be flipped backand forth to alternate between the constant current source (408) duringcharging and the load (414) during discharging.

It is noted that the application of pressure and charging/dischargingmay be performed independently of one another and/or in any desiredcombination. For example, some production processes may include a cyclewhere a charging current is applied while the battery cell isuncompressed. If so, the press may be opened (not shown here) so that nopressure is applied to the battery cell. Then, while the battery cell isuncompressed, a charging current is applied to the battery cell usingthe constant current source (408).

Diagram 420 shows an example of a hot press (424) which applies heatand/or pressure to a battery cell (422) which is inside of the hotpress. Some production steps may include applying heat and/or pressureto the battery cell and the hot press may be used for those steps. Inthis example, the hot press is able to reach temperatures in excess of˜100° C. and pressures of ˜200 psi. The heat and pressure applied areindependent of each other and can be separately controlled so that anydesired combination of heat and pressure (within the supported ranges)is possible.

The following figure gives an example of a battery cell productionprocess with separate preformation and formation steps in order to givecontext to the process of FIG. 1.

FIG. 5 is a flowchart illustrating an embodiment of battery cellproduction process with separate preformation and formation steps. Inthis example, the first step (500) is to fill the battery cell withliquid electrolyte. The battery cells at the beginning of this processhave been partially assembled up to the point where the liquidelectrolyte is about to be introduced into the battery cell. See, forexample, FIG. 2. Once filled with liquid electrolyte, the battery cellwill look like the battery cell shown in diagram 220 in FIG. 2, exceptthe SEI has not yet been formed. In the context of FIG. 1, theelectrolyte fill step is associated with step 100 since the liquidelectrolyte is used to form the SEI.

In one example of step 500, the battery cell is filled at a rate of ˜5mL/Ah. The battery manufacturer may want each battery cell to have somedesired amount of capacity (e.g., in Ah) which in turn dictates how muchvolume of the liquid electrolyte to fill the battery cell with (e.g., inmL). The filled battery cell then rests for ˜2 hours while sealed with aclip and is then vacuum sealed.

The second step is a rest step (502). In one example, the battery cellrests for ˜12-24 hours at an elevated temperature of ˜45° C. The batterycell is then pressed at relatively high pressure (e.g., 100-200 psi) fora brief period of time (e.g., 10-20 seconds) at room temperature so thatthe electrode is flat and not wrinkled. No charge is applied to thebattery cell during this rest step (502).

The third step is the preformation step (504) during which the SEI isgrown. A detailed example of a preformation step is described in moredetail below.

The fourth step is to cure the SEI (506). In one example, the batterycell rests in an oven at a temperature of ˜45° C. for ˜12-24 hours. Thebattery cell is then pressed at a high pressure (e.g., 100-200 psi) fora brief period of time (e.g., 10 seconds) at an elevated temperature(e.g., 10-20 seconds). For example, hot press 424 in FIG. 4 may be used.The applied heat could cause undesirable chemical reactions in thebattery cell if applied for too long of a time so the duration is keptrelatively short (e.g., 10-20 seconds).

The last step (508) is the formation step during which the SEI ischarged and discharged for one or more initial cycles. A detailedexample of a formation step is described below.

The following figure gives a more detailed example of a preformationstep (504).

FIG. 6 is a diagram illustrating an embodiment of a preformation stepduring which a solid electrolyte interface (SEI) is grown. For contextand as a reminder, diagram 600 shows that this example is performedduring a preformation step (602). With regard to FIG. 1, this example isassociated with step 100.

Diagram 620 shows a graph where the x-axis is time and the y-axis is thevoltage of the battery cell. During a first period of time (622) from 0to 100 hours, the cell is charged from its initial voltage to 3.65V(e.g., which causes the SEI to partially grow), the temperature issubstantially at room temperature (e.g., ˜25° C.-50° C.), and thebattery cell is uncompressed.

During the next period of time (624), the battery cell rested from 100hours to t during which no charge is applied to the battery cell and nopressure is applied to the battery cell. In one example, the rest period(624) lasts for a duration of 12 hours.

During the third period (626) from t to t+30 hours (i.e., over a span of30 hours), the battery cell is charged, increasing its resting voltageto 3.85 V (e.g., which further grows the SEI which was partially orinitially grown during period 622), the temperature is substantially atroom temperature (e.g., ˜25° C.-50° C.), and the battery cell iscompressed at a pressure of ˜20 psi-60 psi.

Each time a current is applied and the battery cell's voltage graduallyincreases in this example (e.g., during period 622 and 626), the SEIgrows a little bit more. For example, during the first charging cycle(622), some molecules of the liquid electrolyte change from a liquidstate to a solid state, forming a partial or initial SEI on the SiOanode. This partial or initial SEI is then grown further during thesecond charging cycle (622). To put it another way, as this exampleshows, the SEI may be grown over multiple cycles.

In this example, the battery cell is not compressed during the firstcharging period (622). This may be acceptable because even if theelectrode is slightly or initially wrinkled, the pressure applied duringthe later period of battery cell charging (e.g., 626) is sufficient toflatten the electrode. Naturally, if desired, the battery cell may becompressed during the first period as well.

With regard to the temperature, the battery cell is kept atsubstantially room temperature (e.g., ˜25° C.-50° C.) during the periodsshown (622-626). Heating the battery cell to relatively hightemperatures (e.g., in excess of 60° C.) for prolonged periods of time(e.g., minutes or longer) could cause unwanted and/or undesirablechemical reactions in the battery cell. For this reason, it is desirableto keep the battery cell substantially at room temperature wherepossible.

This example is described more generally and/or formally in flowchartsbelow.

FIG. 7 is a diagram illustrating an embodiment of a process to form asolid electrolyte interface over at least two cycles of battery cellcharging. In some embodiments, the process of FIG. 7 is used to performstep 100 in FIG. 1.

At 700, a partial solid electrolyte interface is formed, including byapplying a first charging current to the battery cell while the batterycell is uncompressed. Period 622 in FIG. 6 shows an example of thiswhere a charging current is applied until the battery cell's voltagereaches 3.65 V. As shown in FIG. 4, in some embodiments, a constantcurrent is applied.

At 702, the solid electrolyte interface is formed from the partial solidelectrolyte interface, including by applying a second charging currentto the battery cell while the battery cell is compressed. Period 626 inFIG. 6 shows one example of this where a charging current is applieduntil the battery cell's voltage reaches 3.85 V.

FIG. 8 is a diagram illustrating an embodiment of a process to form asolid electrolyte interface over at least two cycles of battery cellcharging over different amounts of time and up to different voltages. Insome embodiments, the process of FIG. 8 is used to perform step 100 inFIG. 1.

At 800, a partial solid electrolyte interface is formed, including byapplying a first charging current to the battery cell while the batterycell is uncompressed, wherein the first charging current is applied overa first amount of time and up to a first voltage. See, for example, thefirst battery charge which occurs during period 622 in FIG. 6. In thatexample, the first amount of time=100 hours and the first voltage=3.65V.

At 802, the solid electrolyte interface is formed from the partial solidelectrolyte interface, including by applying a second charging currentto the battery cell while the battery cell is compressed, wherein: thesecond charging current is increased over a second amount of time and upto a second voltage, the first amount of time is greater than the secondamount of time, and the first voltage is less than the second voltage.See, for example, the second battery charge which occurs during period626 in FIG. 6 where the second amount of time=30 hours and the secondvoltage=3.85 V. As specified by step 806, the first amount of time(i.e., 100 hours) is greater than the second amount of time (i.e., 30hours) and the first voltage (i.e., 3.65 V) is less than the secondvoltage (i.e., 3.85 V).

The following figure describes an example of a formation step.

FIG. 9 is a diagram illustrating an embodiment of a formation stepduring which an electrode is charged for the first time. For context andas a reminder, diagram 900 shows that this example is performed during aformation step (902).

Diagram 920 shows a graph where the x-axis is time and the y-axis is thevoltage of the battery cell. During a first charging period (922), acharging current is applied to the battery cell until the voltage hasincreased to a first voltage (V₀) from time 0 to 20 hours which chargesthe battery cell for a first time. In this example, V₀ is in the rangeof ˜2.0V to 4.4V. The battery is then discharged during a firstdischarge period (924) during which time no voltage is applied. Forexample, in diagram 400 in FIG. 4, the switches (412) would beconfigured so that the battery cell (402) is able to pass charge to theload (414).

During a second charging period (926), a charging current is againapplied until the battery cell's voltage has increased to a secondvoltage (V₁) over a period of 10 hours. In this example, V₁ is in therange of ˜2.5V to 4.4V. The battery cell is then discharged during asecond discharge period (928).

During a third charging period (930), a charging current is applied toincrease the battery cell's voltage to a third voltage (V₂) over aperiod of 5 hours. In this example, V₂ is in the range of ˜2.8V to 4.4V.

In this example, the temperature is kept substantially at roomtemperature (e.g., in the range of ˜25° C.-50° C.) during all of theperiods shown here (922-932). As described above, if the battery cell istoo hot (e.g., in excess of 60° C.) for too long of a time (e.g.,minutes or longer), undesirable chemical reactions may occur in thebattery cell and for this reason it may be desirable where possible toperform steps at room temperature.

In this example, the battery cell is compressed during all of theperiods shown here (922-932), for example in the range of ˜20 psi-60psi. This pressure helps to keep to keep the electrode flat and preventswrinkling. Even though the SEI has already formed at this point, thefirst few cycles of charging after the SEI has formed are importantbecause the electrode could still wrinkle (e.g., because the SEI has notyet hardened and/or set). Since the materials in the battery cell arecontinually expanding and contracting (with some materials expanding andcontracting a great deal, and some other materials not expanding andcontracting as much) an unstable SEI could still cause the electrode towrinkle. By applying pressure during these first few cycles of charging(e.g., where the SEI is being electrically exercised for the first fewtimes), the SEI will “harden” into a good shape where the electrodeshave good proximity to each other.

This example is described more generally and/or formally in a flowchartbelow.

FIG. 10 is a flowchart illustrating an embodiment of a process to chargean electrolyte for one or more initial cycles while a battery cell iscompressed. In some embodiments, the process of FIG. 10 is performedduring step 102 of FIG. 1.

At 1000, a first charging current is applied to the battery while thebattery cell is compressed, wherein the first charging current isapplied over a first amount of time and up to a first voltage. See, forexample, the first charging period (922) in FIG. 9.

At 1002, a second charging current is applied to the battery cell whilethe battery cell is compressed, wherein: the second charging current isapplied over a second amount of time and up to a second voltage, thefirst amount of time is greater than the second amount of time, and thefirst voltage is less than or equal to the second voltage. See, forexample, the second charging period (926) in FIG. 9. As specified bystep 1002, the first amount of time (i.e., 20 hours) is greater than thesecond amount of time (i.e., 10 hours) and the first (ceiling) voltage(in that example, between 2.0V and 4.4V) is less than or equal to thesecond (ceiling) voltage (in that example, between 2.5V and 4.4V).

In some embodiments, a battery cell is briefly compressed at arelatively high pressure at various times to produce a flat electrode.The following figure shows an example of this.

FIG. 11 is a diagram illustrating an embodiment of a high pressure step.In the example shown, a first high pressure step (1100) occurs during anSEI curing step (1102). During this first high pressure step, thebattery cell is compressed at ˜100-200 psi, substantially at roomtemperature (e.g., ˜25° C.-50° C.), and for a relatively short duration(e.g., ˜10-20 seconds).

With regard to other steps in the SEI curing step (1102), the highpressure step (1100) occurs after all other steps have occurred, forexample, after letting the battery cell rest for 12-24 hours at elevatedtemperatures in an oven. To put it another way, high pressure step 1100occurs right before the formation step (1106).

A second high pressure step (1104) occurs during the formation step(1106). During this second high pressure step, the battery cell iscompressed at ˜100-200 psi, at an elevated temperature (e.g., ˜60°C.-100° C.), and for a relatively short duration (e.g., ˜10-20 seconds).In some embodiments, this temperature range (i.e., ˜60° C.-100° C.) isused because it is hot enough to soften SEI (which is in solid form) sothat the electrode can be pressed flat while still minimizing anyundesirable chemical reactions in the battery cell. As described above,this temperature range (e.g., ˜60° C.-100° C.) may cause undesirablechemical reactions in the battery cell and therefore this step onlylasts for a brief period of time.

With regard to other steps in the formation step (1106), the highpressure step (1104) occurs after all other steps have occurred, forexample, after compressing and charging/discharging the battery cellmultiple times. For example, with regard to FIG. 9, the second highpressure step (1104) shown here may occur after the charging anddischarging shown in FIG. 9.

Briefly compressing the battery cell throughout the production process(one example of which is shown here) may help to produce a flatelectrode.

This example is described more generally and/or formally in a flowchartbelow.

FIG. 12 is a flowchart illustrating an embodiment of a process toproduce a wrinkle-free silicon monoxide electrode using separatepreformation and formation steps and brief, high compression steps. FIG.12 is related to FIG. 1 and identical reference numbers are used toindicate identical steps.

At 100, a solid electrolyte interface is formed on a silicon monoxideelectrode in a battery cell. See, for example, the preformation exampleshown in FIG. 6.

At 1200, after the solid electrolyte interface is formed on the siliconmonoxide electrode and before the battery cell is charged for one ormore initial cycles, the battery cell is compressed at room temperature.See, for example, high compression step 1100 in FIG. 11.

At 102, after the solid electrolyte interface is formed on the siliconmonoxide electrode, the battery cell is charged for one or more initialcycles while the battery cell is compressed. See, for example, theformation example shown in FIG. 9.

At 1202, after the battery cell is charged for one or more initialcycles, the battery cell is compressed while the battery cell is heated.See, for example, high compression step 1104 in FIG. 11.

Although the foregoing embodiments have been described in some detailfor purposes of clarity of understanding, the invention is not limitedto the details provided. There are many alternative ways of implementingthe invention. The disclosed embodiments are illustrative and notrestrictive.

What is claimed is:
 1. A method, comprising: forming a solid electrolyteinterface on a silicon monoxide electrode in a battery cell; and afterthe solid electrolyte interface is formed on the silicon monoxideelectrode, charging the battery cell for one or more cycles while thebattery cell is compressed, including by: applying a first chargingcurrent to the battery cell while the battery cell is compressed,wherein the first charging current is applied over a first amount oftime and up to a first voltage; in response to the battery cell reachingthe first voltage, discharging the battery cell while the battery cellis compressed; after the first charging current has been applied and thebattery cell has been discharged, applying a second charging current tothe battery cell while the battery cell is compressed, wherein: thesecond charging current is applied over a second amount of time and upto a second voltage, the first amount of time is greater than the secondamount of time, and the first voltage is less than or equal to thesecond voltage; and in response to the battery cell reaching the secondvoltage, discharging the battery cell while the battery cell iscompressed.
 2. The method recited in claim 1, wherein forming the solidelectrolyte interface includes: forming a partial solid electrolyteinterface, including by applying a third charging current to the batterycell while the battery cell is uncompressed; and forming the solidelectrolyte interface from the partial solid electrolyte interface,including by applying a fourth charging current to the battery cellwhile the battery cell is compressed.
 3. The method recited in claim 1further comprising: after the solid electrolyte interface is formed onthe silicon monoxide electrode and before the first and the secondcharging currents are applied and the battery cell is discharged inresponse to the battery cell reaching the first and the second voltage,compressing the battery cell at room temperature; and after the firstand the second charging currents are applied and the battery cell isdischarged in response to the battery cell reaching the first and thesecond voltage, compress the battery cell while the battery cell isheated.
 4. The method recited in claim 1, wherein forming the solidelectrolyte interface includes: forming a partial solid electrolyteinterface, including by applying a third charging current to the batterycell while the battery cell is uncompressed, wherein the third chargingcurrent is applied over a third amount of time and up to a thirdvoltage; and forming the solid electrolyte interface from the partialsolid electrolyte interface, including by applying a fourth chargingcurrent to the battery cell while the battery cell is compressed,wherein: the fourth charging current is applied over a fourth amount oftime and up to a fourth voltage, the third amount of time is greaterthan the fourth amount of time, and the third voltage is less than thefourth voltage.
 5. The method recited in claim 1, wherein: forming thesolid electrolyte interface includes: forming a partial solidelectrolyte interface, including by applying a third charging current tothe battery cell while the battery cell is uncompressed; and forming thesolid electrolyte interface from the partial solid electrolyteinterface, including by applying a fourth charging current to thebattery cell while the battery cell is compressed; and the methodfurther includes: after the solid electrolyte interface is formed on thesilicon monoxide electrode and before the first and the second chargingcurrents are applied and the battery cell is discharged in response tothe battery cell reaching the first and the second voltage, compressingthe battery cell at room temperature; and after the first and the secondcharging currents are applied and the battery cell is discharged inresponse to the battery cell reaching the first and the second voltage,compress the battery cell while the battery cell is heated.
 6. Acomputer program product, the computer program product being embodied ina non-transitory computer readable storage medium and comprisingcomputer instructions for: forming a solid electrolyte interface on asilicon monoxide electrode in a battery cell; and after the solidelectrolyte interface is formed on the silicon monoxide electrode,charging the battery cell for one or more cycles while the battery cellis compressed, including by: applying a first charging current to thebattery cell while the battery cell is compressed, wherein the firstcharging current is applied over a first amount of time and up to afirst voltage; in response to the battery cell reaching the firstvoltage, discharging the battery cell while the battery cell iscompressed; after the first charging current has been applied and thebattery cell has been discharged, applying a second charging current tothe battery cell while the battery cell is compressed, wherein: thesecond charging current is applied over a second amount of time and upto a second voltage, the first amount of time is greater than the secondamount of time, and the first voltage is less than or equal to thesecond voltage; and in response to the battery cell reaching the secondvoltage, discharging the battery cell while the battery cell iscompressed.